https://bugs.llvm.org/show_bug.cgi?id=50635
Bug ID: 50635
Summary: [11->12 regression] Improper assignment fusion
Product: new-bugs
Version: unspecified
Hardware: PC
OS: Linux
Status: NEW
Severity: enhancement
Priority: P
Component: new bugs
Assignee: unassignedb...@nondot.org
Reporter: blub...@gmail.com
CC: htmldevelo...@gmail.com, llvm-bugs@lists.llvm.org
To reproduce:
#include <stdint.h>
struct S1 {
uint8_t val1;
uint8_t this_gets_clobbered;
uint16_t val2;
};
void test(S1 src, S1* dest) {
dest->val1 = src.val1;
dest->val2 = src.val2;
}
Compile with -O1 or higher, with Clang 12.0.0 or higher (codegen is proper on
11.0.1).
Expected result:
test(S1, S1*): # @test(S1, S1*)
mov byte ptr [rsi], dil
shr edi, 16
mov word ptr [rsi + 2], di
ret
Actual result:
test(S1, S1*): # @test(S1, S1*)
mov dword ptr [rsi], edi
ret
Compiler Explorer: https://godbolt.org/z/1W1oKdfcG
Found by user @fifty#1323 on Discord.
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